1. Field of the Invention
This invention concerns a gas-dynamic pressure wave machine for the charging of an internal combustion engine in which, within the gas chamber, an exhaust gas bypass with a medium-controlled flap connects the high pressure gas supply duct with the low pressure gas escape duct.
2. Description of the Prior Art
The application of an exhaust gas bypass can be quite interesting in small engines for passenger cars being charged by means of pressure wave machines in which the peak pressure is limited and which have a wide speed range. Since such engines have an elastic torque which is characterized by flat pressure development across the entire engine speed range, on the one hand, in comparison with the exhaust gas turbocharging, less exhaust gas must be released into the exhaust pipe and, on the other hand, the release must only take place with higher engine speeds. Thus, the poorer specific fuel consumption caused by the non-utilized release occurs only in a narrow range which, according to experience, is a rare event in the case of passenger cars.
The control of the charged air pressure by a targeted release is known for a pressure wave machine as mentioned in the introduction from the British Pat. No. 775,271. When the exhaust gas pressure exceeds a predetermined value, a spring-loaded flap is opened which is arranged between the high pressure gas supply duct and the lower pressure gas escape duct in a bypass. A portion of the exhaust gas enters the exhaust pipe directly through this bypass without passing through the pressure wave process.
Since this known release control always operates only with a permanently set excess pressure even when driving uphill, the bypass is opened too early under these conditions so that the final pressure required for the acceleration processes is not reached with a rising level owing to the reduced air density.